A switching device of this kind is presented for example in U.S. Pat. No. 6,388,867 B1. A circuit breaker is presented there, which has a hood arrangement to guide the arc gases out of the housing. An arc which forms between the contacts of a contact pair of the circuit breaker is extinguished within the housing of the circuit breaker. For the duration of the arc, gases are released at high pressure and high ionization level; and these gases exit the housing through openings in an upper wall of the housing. The openings of several switching chambers of different current paths are arranged side by side. The openings are covered by a hood, which forms a channel for two exhaust openings facing away from each other. Hereby, all openings lead into the channel which goes through the hood. Thus, the highly ionised arc gases are led out or blown out of the housing from two sides.
Switching devices can generate a large quantity of arc gases when interrupting high currents and voltages. Arc gases are usually exhausted through the upper or rear side of the switching device. Electrical switching devices typically include many current paths (poles), and therefore, particularly in case of short circuits, flash-overs can occur during the blowing out of arc gases in the proximity of a terminal contact of a current path. In the switching device in accordance with U.S. Pat. No. 6,388,867 B1, flash-overs are prevented by exhausting the arc gases at the sides of the housing which are arranged as far away as possible from the terminal contacts.
In principle, switching devices are required in case of a short circuit to remain intact and flash-overs between different current paths (poles) should be avoided. The measures implemented for preventing the destruction of the housing of the switching device are: selection of suitable materials for the switching chambers and their wall thicknesses as well as the selection of the appropriate pressure release openings or exhaust openings which, particularly in the case of short circuits, blow out arc gases that form explosively. Short circuit currents that occur in direct current applications are difficult to control due to the fact that in this case there is no natural zero passage which would quickly interrupt the arc and therefore cause a permanent interruption of the circuit. Very compact switching devices exist, and these have short paths, which can easily be bridged over electrically by highly ionized arc gases and can consequently lead to flash-overs. Therefore, in very compact switching devices, flash-overs can occur between different contact pairs if highly ionized arc gases exit out of the housing and thereby bridge over several different switching chambers as in the case of a short circuit.